Which description correctly matches preload and afterload?

• A. Preload - end diastolic volume; Afterload - total peripheral resistance
• B. Preload - total peripheral resistance; Afterload - end diastolic volume
• C. Preload - stroke volume; Afterload - heart rate
• D. Preload - cardiac contractility; Afterload - ejection fraction

Answer: (A)

Preload reflects how much the ventricle is stretched at the end of filling, which is best described by the end-diastolic volume. Afterload is the pressure the ventricle must overcome to eject blood, which is governed mainly by the arterial pressure and the resistance in the systemic circulation, i.e., total peripheral resistance. So preload aligns with end-diastolic volume, and afterload aligns with total peripheral resistance.

Think of preload as the filling state that stretches the heart muscle before it contracts, while afterload is about the pressure the heart works against when pushing blood out. The other ideas don’t fit: stroke volume is the output influenced by preload and afterload, not a definition of preload; heart rate is a separate factor unrelated to preload/afterload; contractility is the heart’s intrinsic squeeze, not a measure of preload; and ejection fraction is a readout of systolic performance, influenced by both loads and contractility, not a direct descriptor of afterload.